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'91 LT4WDX 4x4 Quadrunner - No Spark

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'91 LT4WDX 4x4 Quadrunner - No Spark

Old 01-04-2019, 03:07 PM
Weekend Warrior
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Join Date: Dec 2006
Posts: 4
Default '91 LT4WDX 4x4 Quadrunner - No Spark

I've searched the forum to see if I could find info that would help me with my issue. Loads of useful info but still wasn't able to solve my issue.
I'm working on my neighbor's 1991 LT-4WDX Quadrunner.
VIN: JSAAK42A1M2104190 (8th letter could be a "4")
He says he hit a snow bank when plowing, the machine died and hasn't sparked since. The owner was told that these quads were famous for skipping the timing chain. Not sure if this is true or not but in any case I would still get a spark even if the timing was not correct. Plus, as far as I know, the timing chain also runs the camshaft that opens/closes the valves...and there is compression. I checked out the coil and found the secondary resistance readings were out. Replaced the coil and expected to see a spark. There was none!
I've checked the integrity (resistance) of the wiring from;
1) coil signal wire back to CDI box connection - good.
2) pickup coil wiring to CDI box connections - good (112 Ohms between wires with no continuity to ground)
3) lighting coil wires (3 yellow) to rectifier box connections - 1.7 Ohms between each wire, no continuity to ground)
4) 12-volt feed wire going to CDI box - good

When I turn it over should I be able to read AC or DC voltage from one of the wires coming from the pickup coil (pulse generator)? As well, should there be DC voltage coming from the signal wire on the CDI box going to the coil terminal? Is there a way to check the CDI box? Looks like I've ruled out any other possibilities.... I think!

My suspicion is that the pickup coil is not giving a signal but I have no idea on how to confirm this. Is the pickup coil location adjustable....wondering if the bolts are loose and the distance is too great to create a signal.
I appreciate any help given in solving the above no-spark issue.
Old 01-05-2019, 04:16 AM
Extreme Pro Rider
Join Date: Oct 2013
Location: Lancaster England
Posts: 3,522

The voltage from the pickup coil (Trigger) can be quite low, so is difficult to read. A device called a peak voltage tester plugs into your standard multi meter instead of the normal leads, to test the exciter and trigger coil voltages, I have trouble getting that to give a decent reading too. First change the plug, if you haven't already, after that check all the wires going to the CDI, it is just as likely to be the kill wire or earth that is faulty as the wires to the stator. Check the outside of the CDI, a blown CDI often shows visible signs, like a blister on the case. If everything checks out and still no spark, you are left with substitution, either CDI, trigger, or stator, get it wrong and you have spent a lot for nothing. I don't know the 1990s Suzukis too well, but adjustable trigger coils mostly stopped being used in the mid 80s, it may have come loose.
Old 01-05-2019, 09:57 PM
Weekend Warrior
Thread Starter
Join Date: Dec 2006
Posts: 4

Thanks for the input Merryman.
I'm going back to my garage tomorrow to double-check all the wiring, do a visual on the CDI box and then start by changing out the CDI box.
Old 01-06-2019, 04:49 AM
Extreme Pro Rider
Join Date: Oct 2013
Location: Lancaster England
Posts: 3,522

Don't forget to check that earth wire and kill wire to the CDI first, a dud earth can kill a new CDI.
Old 01-06-2019, 05:47 PM
Weekend Warrior
Thread Starter
Join Date: Dec 2006
Posts: 4

- ignition switch, Run/Stop and Starter button wiring - all good. Power is supplied to starter, neutral relay, and CDI box
- wiring (2) and electrical plug continuity coming from pickup coil to CDI box - all good
- wiring (3) and electrical plug continuity from stator to regulator/rectifier - all good
- hot wire from ignition switch to regulator/rectifier - battery power
- ground wire on reg/rectifier - good
- CDI ground wire and plug - continuity to ground & continuity on both sides of plug-
- hot wire coming from run/stop switch - battery power when in Run
- ignition coil ground wire - continuity between frame, coil mounting bracket and ground wire
- wire coming from CDI box to ignition coil signal terminal - CDI plug, wire and ignition coil terminal all have continuity.

Should there be battery voltage going down the signal wire coming from CDI box to the ignition coil when I crank the engine?
Since I've ruled out all of the wiring and connectors, I will start shopping for a CDI box tomorrow. Hope to be able to find a used unit.
I read online that someone had warmed up a faulty CDI box and got it to work temporarily just to prove it faulty. I tried that but was unsuccessful.
Old 01-07-2019, 04:30 AM
Extreme Pro Rider
Join Date: Oct 2013
Location: Lancaster England
Posts: 3,522

The problem is, without the wiring diagram, I'm unsure what system you have, from your readings, it looks like you have either a DC ignition system, like pre fuel injection cars, or a hybrid system, Honda used this type on 300 and 350 models. Hybrids are so complex that I would advise getting the manual and checking your readings against that, if everything checks out, then you are left with it being a CDI problem.
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